1. Field of the Invention
The present invention relates to a device and method for clamping and grounding a cable, and in particular, to a device and method that clamps a periphery of the cable to ground the cable to a frame through which the cable passes, to prevent electromagnetic radiation leakage.
2. Background Information
Computer systems may include a number of interconnected subsystems. A typical subsystem may include a system frame containing a system processor, for example, and/or other electrical components, such as printed circuit boards, that are electrically coupled to associated electrical components disposed in other subsystems.
Electrical cables, such as coaxial cables, may be used to electrically couple the respective electrical components of the various subsystems. For example, the electrical cables typically will have an internal conductive (signal) wire that allows electrical signals, for example, to be transmitted from one printed circuit board to another printed circuit board. This allows various electrical components on the one printed circuit board to communicate with electrical components on the other printed circuit board. Cables are also used to transmit power to and from the various electrical components.
Many of the electrical components inside the respective subsystems, when operated, will generate emissions that include electromagnetic radiation. This electromagnetic radiation may travel through the air, and be received by the electrical components of the other subsystems, and/or by the signal wires of the cable. The received electromagnetic radiation may then adversely affect the operation of the various electrical components (to which the cable may or may not be connected), causing the computer system to malfunction. When this electromagnetic radiation adversely influences the proper functioning of the electrical components, the result is known as electromagnetic interference (also known as EMI). Thus, in order to ensure reliable operation, cables have been developed in which the signal wire or wires within the cable are shielded against outside interference. For example, it is known to wrap or encircle all of the signal wires in a cable by a conducting shield, usually a conductive foil surrounded by a conductive braided wire. Typically, the conducting shield is covered with an outer insulating sheathing (cover), and is connected to an external jacket, such as a metal housing shield of a plug, at each end of the cable. The metal housing shield is then coupled to a ground potential, so that any electromagnetic radiation is conducted to the ground potential, thereby preventing the radiation from being received by the signal wires and adversely affecting the electrical components coupled to the cable.
However, while the above approach will effectively shield the signal wires of the cable, unless adequately protected, the various electrical components of one subsystem may still be affected by the electromagnetic radiation emitted from another subsystem. Thus, it is also conventional to provide an EMI shield around each respective subsystem, so that the electromagnetic radiation emitted from an electrical component in one subsystem will not adversely affect the electrical components in the other subsystems. This can conventionally be accomplished by completely enclosing each subsystem with a conductive frame that is coupled to a ground potential, so that any electromagnetic radiation is conducted, via the frame, to the ground potential. In order to prevent electromagnetic radiation from leaking from the subsystem, it is also conventional to overlap adjoining edges of the conductive frame, and/or to provide a conductive compressive gasket in seams formed between the adjoining edges of the frame.
However, as will be appreciated, the cable or cables that are used to couple the electrical components of one subsystem with the electrical components of the other subsystems must pass through the frames of the respective subsystems. This could be accomplished simply by forming an opening in the sides of the respective frames, and extending the cables through the openings. However, electromagnetic radiation may also pass through the openings. As such, this approach is not satisfactory when complete sealing of the respective subsystems against electromagnetic radiation leakage is desired.
It is thus also conventional to provide cable connectors that are attached and grounded to the sides of the respective frame. Each cable connector may have opposing cable ports, with one of the ports (the inside port) being accessible from inside the subsystem frame, and with the other port (the outside port) being accessible from outside the subsystem frame. Each port includes an external conductive jacket that is coupled to earth ground and that can be coupled to the shield of the cable, and an inner connector that can be coupled to the signal wires of the cable. Using this approach, a first cable is used to connect an associated electrical component to the inside port, and a second cable is used to connect the outside port of the connector to an outside port of another connector disposed on another subsystem frame.
However, cable connectors are relatively expensive. As such, this approach may cause an unacceptable increase in the overall cost of the system. Moreover, since the cables will need to be individually connected, using cable connectors will increase the time required to assemble a system, which again may cause an unacceptable increase in the overall cost of the system. Thus, there is a need for an arrangement that will allow a cable to connect the electrical components of one subsystem with the electrical components of another subsystem without the use of conventional cable connectors at the subsystem boundaries.
Additionally, the numerous cable connections that are required significantly increase the likelihood that a connection will fail, thus reducing the reliability of the resulting system. Thus, there is a need for a way to allow a cable to reliably connect the electrical components of one subsystem with the electrical components of another subsystem.
Further, with larger and more complex systems, it is typical to require numerous, for example, 10, 20 or 30 or more, cables per subsystem. With a large number of cables, it may be impossible to provide a large enough surface area on the frame that could accommodate the necessary number of cable connectors.
Thus, there is a need for an arrangement that will easily accommodate multiple cables to connect the electrical components of one subsystem with the electrical components of other subsystems.